In the field of power transmission, efficient transmission of power from a power source to a load requires that impedance at the load be reasonably matched to the characteristic impedance of the transmission line which connects power source to load. Such a match is desirable not only from the point of view of efficiency but also to prevent damage to the power source due to the reflected power caused by a mismatch.
The problem of mismatch is one of long standing and has been solved in various ways. For example, one type of system senses mismatch and varies the gain of the power source accordingly. Another type of system changes the impedance of the load until the mismatch is corrected. Most of these systems work well in their environment which may be, e.g., supplying R.F. power to a transmitting antenna.
The present invention is an R.F. impedance match control system ideally suited for use in plasma etching systems wherein mismatch detection and correction is done in time controlled sequences.